Clinical techniques to diagnose abnormal wrist joint motion are highly subjective and have a high false positive rate. Additionally, routine radiographic examinations cannot demonstrate dynamic wrist instabilities. This is a significant clinical problem, since individuals suffering from wrist joint instabilities experience progressive degenerative disease that leads to functional disabilities and osteoarthritis (OA). The associated pain prevents them not only from conducting important occupational tasks, but often simple activities of daily living. However, if physicians are able to diagnose dynamic joint instabilities at an early stage, surgical intervention can restore normal function before the onset of arthritis or static deformities. Thus, to have a critical impact on clinical outcomes, a method that allows early detection of functional wrist joint abnormalities is desperately needed. To address this significant public health problem, the long-term goal of our team is to non-invasively diagnose and quantify subtle dynamic joint instabilities of the wrist that can only be observed during joint motion. We have shown that we can meet this critical need using four-dimensional (4D;3D + time) CT imaging techniques. Based on our successful preliminary work, our central hypothesis is that we can non-invasively determine the complex motion paths of the carpal bones using 4D CT imaging techniques. Our objective in this application is to develop a practical 4D CT examination to detect abnormal wrist joint motion occurring as a result of scapholunate instability. Specifically, in Aim 1, we will develop a robust low dose 4D CT imaging technique to image joint motion in the wrist. Our working hypothesis is that low dose dual-source CT can provide artifact-free images of the moving wrist, at velocities similar to those of activities of daily living. We will develop biomechanical motion devices to test this hypothesis in cadaveric specimens, and determine the minimum radiation dose levels. In Aim 2, we will measure the accuracy and precision of the developed techniques using cadaveric specimens, an optical-based motion analysis system, image registration techniques, and a custom motion simulator. Finally, in Aim 3, we will determine the clinical feasibility of 4D CT wrist joint imaging in asymptomatic subjects and subjects with joint instability. The innovation of this proposal is the use of state-of-the-art CT technology to provide a robust, low dose imaging technique capable of detecting dynamic wrist joint instabilities. We expect three important outcomes: 1) an optimized low dose clinical CT technique for the quantification of wrist articulation, 2) accuracy and precision data for the developed technique, and 3) the first in vivo 4D assessments of wrist joint articulation in both symptomatic and asymptomatic human subjects. These data will provide the foundation for clinical trials to quantify normative and pathologic wrist joint motion. The significance of this proposal is that by diagnosing dynamic wrist joint instabilities at an early stage, intervention to restore normal motion can markedly reduce the human suffering, loss of productivity, and personal and societal costs associated with OA of the wrist. PUBLIC HEALTH RELEVANCE: The goal of this proposal is to design a computed tomography exam (CT, or CAT scan) that can take highly-detailed pictures of the wrist joint while the patient is moving the joint. These three-dimensional movies of the patient's bones can be played back, looking at the joint from any angle, to let the physician see and measure exactly how the surfaces of the bones move. This is very important because abnormal joint motion, which is currently very hard to accurately diagnose, can lead to pain, arthritis or crippling deformities when left untreated.